Programmable power supplies and brownout detectors for electronic equipment, i.e., both digital and analog, are known in the art. The use of electronic equipment in high reliability applications has created the need to change operating voltages to reduce current consumption for low power and battery powered applications. A need also exists to detect when the operating voltage drops below a predetermined level for reliability considerations.
A brownout is considered to have occurred when the incoming voltage available to the electronic equipment has dropped to a level where the electronic circuits should not continue operating, since errors or partly functional conditions may occur in case of digital circuit logic or storage elements. The brownout ends when the voltage has risen back above the brownout level. A hysteresis or latching scheme can be used to prevent oscillation at the brownout level. A brownout detector detects when the operating voltage has dropped to just above the brownout voltage level and produces a signal to indicate to the electronic equipment that a brownout is pending. The brownout detector can reset or freeze the operation of the electronic equipment to avoid improper operation.
In a practical application, the electronic equipment must be protected against brownout conditions that can cause digital logic to enter unknown states and thereby corrupt the operation of the electronic equipment, and/or analog circuit latch-up or saturation conditions. In the existing state of the art, these power supplies and brownout detectors are either not linked in operation at all, or are linked only by virtue of the reference voltage to the brownout detector being related directly to the operating voltage to the electronic equipment. Also there is no provision for lowering the operating voltage of the electronic equipment during sleep mode to reduce current consumption.